Above is a good write up on how to install Air bags in the rear and how to create minor lift on an AWD system. Some use a hand or local gas station compressor. Others have onboard compressors in their van. Excellent install and "opening post write up".
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On my 2001 AWD Safari van, I also lifted in front via torsion bars adjustment. Over time, my van's torsion bars started to loose their support strength, and its front starts to natually go down. Visualize "front end" sag. Adjusting its torsion bars to make the van's "stance" look better is a good thing to do. And if natural sag over time (like with my van), adjusting its front torsion bars to make its front axle alignments more horizontal is a good idea. Having horizontal front axles creates less front CV, bearing and boot wear. After Torsion bar adjustments, a wheel alignment is always recommend. Great idea....
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With or without ground height adjusted height front end, another rear suspension improvement product is Timbrens. From a white board visual, Timbens are like air bags without the pressurized air inside them. Without air, there's no fussing with different lbs pressure and best part of all, they are an "install it and leave it" suspension improvement product. For me, I installed Timbrens SES 2,000 lbs in the rear of my 2001 AWD Safari myself - under 15 minutes. Their van's empty ride is NOT changed. When the rear of the van goes down 1/2", the Timbrems start to do their magic. The more the van's rear goes down, the more progressive the Timbrens become. For anyone wanting to perform extra hauling, towing or elimiante "factory mush" rear suspension, do look at the Timbren product. Glad I have them on my Safari street van. For details, surf:
http://www.timbren.com/ses-van-suv.htm
Note: Just like air bags, do remember to install/use a WDH (Weight Distribution Hitch) system when towing heavy weight trailers. Especially when a trailer's weights are above the non-distribution weight numbers of your van's hitch. The air bags or Timbrens are used to "enhance / improve" the existing factory system. Especially for internal cargo and for non-WD Hitch trailer towing.
Hope this helps as well...
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